1. Field the Invention
The present invention relates to the depropanizing of unreacted benzene from the alkylation of benzene to produce cumene. More specifically the invention relates to the recovery of benzene from the overhead product of a distillation column reactor which produces cumene. In one embodiment the present invention relates to an integrated process for the production of cumene from the alkylation of benzene with propylene.
2. Related Information
Recently a new process has been developed for the production of cumene from the reaction of benzene and propylene. The new process utilizes a distillation column reactor to react benzene with propylene and simultaneously separate the higher boiling product cumene from unreacted benzene and C.sub.3 's. In the preferred embodiment of the process the propylene, which is stored as a liquid, is vaporized and fed to the distillation column reactor as a gas to assure proper propylene/benzene mixing.
In the alkylation of benzene with an olefin in a distillation column reactor, the prior art shows the unreacted olefin (ethylene or propylene for example) being separated from the benzene in the overheads by partial condensation of the benzene and the use of a separator-reflux drum. See for example U.S. Pat. Nos. 4,849,569; 4,950,834; 5,019,669; 5,043,506; 5,055,627; 5,080,871; 5,086,193; 5,113,031; 5,176,883; 5,215,725; and 5,243,115 all commonly assigned.
Particularly in the alkylation of benzene with propylene it has been found to be more desirable to separate the unreacted C.sub.3 's from the unreacted benzene by further fractional distillation in a depropanizer column.
The operating pressure of the depropanizer is dependent upon the temperature of the cooling medium in the overhead condenser. An advantage of the present invention is to obtain lower overhead temperatures which result in lower operating pressures in the depropanizer and thus lower heat requirements in the depropanizer reboiler. A further advantage is that the liquid propylene is vaporized as necessary for use in the alkylation with heat from the depropanization that would otherwise be wasted.